1. Field of the Invention
The present invention relates to a differential limiting torque control system for a limited slip differential employed between right and left drive road wheels of an automotive vehicle, in which a differential limiting torque of the limited slip differential is electronically controlled by adjusting an engaging force of a clutch device operably arranged between a differential case and differential side gears, based on an acceleration-state indicative information such as a depression of an accelerator pedal or a throttle opening called an accel opening, and a longitudinal acceleration exerted on the vehicle body.
2. Description of the Prior Art
Recently, there have been proposed and developed various differential limiting torque control systems for automotive vehicles, in which a differential limiting torque is variably controlled depending on input information representative of an acceleration state of the vehicle. One such conventional automobile differential limiting system has been disclosed in Japanese Patent Provisional Publication No. 61-102321. For instance, the above-noted conventional system electronically adjusts the differential limiting torque so that the differential limiting torque is increased in accordance with an increase in accelerating degree of the vehicle such as a depression amount of the accelerator pedal. The acceleration state indicative information is correlated to an acceleration component acting in a longitudinal direction of the vehicle. In particular, in the event that the accelerator pedal is excessively depressed when the vehicle turns to the right or to the left on low-frictional roads, there is a possibility that the vehicle will experience an undesired rapid change in its behaviour, so-called power oversteer. As is well known, during cornering, more of the car weight is transferred to the outer wheels and thus the car weight becomes less at the inner wheels owing to such load shift. As a result, the lower-loaded inner wheel tends to slip. In this conventional differential limiting torque control system, in case that the differential limiting torque is rapidly increased due to excessive depression of the accelerator pedal when the vehicle is operating in a cornering critical region, an engine power, i.e., a road-wheel driving torque is transferred from the lower-loaded inner drive-wheel to the higher-loaded outer drive-wheel. This results in a rapid drop in cornering force acting between the outer drive-wheel and the road surface. Consequently, power oversteer tends to occur owing to excessive acceleration in the cornering critical region.